1. Field
The present disclosure relates generally to generating optimized stereo settings for computer animation, and more specifically to calculating scaled bounded-parallax constraints for a computer-generated object in view of a pair of stereoscopic cameras within a computer-generated scene.
2. Related Art
Cinematographic-quality computer animation has evolved to produce increasingly realistic and engaging visual effects. One way that this is accomplished is through the use of stereoscopic filming techniques that simulate human binocular vision by presenting slightly different viewpoints of a scene to a viewer's left and right eye. This technique, also known colloquially as “3D,” can be used to enhance the illusion of depth perception and make objects in a computer-generated scene appear to extend outward from a two-dimensional screen.
In normal human binocular vision, each eye views the world from a slightly different perspective. The difference in the view from each eye, also called parallax, is caused, in part, by the spatial separation between the eyes. In general, the amount of parallax is increased for objects that are closer to the viewer as compared to objects that are further from the viewer. The brain is able to combine the different views from each eye and use the parallax between views to perceive the relative depth of real-world objects.
Computer-animation stereoscopic filming techniques take advantage of the brain's ability to judge depth through parallax by presenting separate images to each eye. Each image depicts a computer-generated object from a slightly different viewpoint. The distance between the left and right images displayed on a screen (parallax) indicates the relative depth of the displayed computer-generated object. Parallax can be positive or negative depending on whether the computer-generated object appears to be behind the screen (positive parallax) or if it appears to be in front of the screen (negative parallax).
In the real world, the amount of parallax between a viewer's left and right eyes is determined by two parameters, which are essentially fixed: the spacing between the eyes of the viewer and the distance from the viewer to the object. However, when composing stereo for a computer-animated scene, a film maker (e.g., a director or stereographer) can adjust a broader range of stereoscopic parameters (scene parameters) to control the perception of depth in a computer-generated scene. In particular, a film maker may be able to adjust scene parameters that determine the camera position, camera separation, camera convergence, and focal length of the lens to increase or decrease the stereo effect (perceived depth of a computer-generated object in a computer-generated scene).
However, providing too much flexibility in the variability of too many scene parameters may make it difficult for the film maker to control or optimize the stereo effect for each shot in a computer-animated sequence. In one traditional solution, many of the scene parameters are fixed or only allowed to vary within a range of hard limits. The fixed values or hard limits serve as a rule-of-thumb for filmmakers, but do not guarantee that stereo effect is satisfactory or comfortable to view by an audience. Additionally, limiting the scene parameters to a fixed value or fixed range of values may under-utilize the design space when composing a computer-generated scene. In particular, fixed ranges limit the film maker's ability to make trade-offs between the interrelated scene parameters, which may limit the ability to produce dynamic three-dimensional effects.
Another traditional solution is to provide the director or stereographer with direct control over the scene parameters for each scene in a film. This approach also has drawbacks in that it may be difficult to fine tune all of the scene parameters to achieve the desired amount of stereo effect. Too little stereo effect and the objects in the scene will appear flat. Too much stereo effect and the objects may appear distorted or the scene may become uncomfortable to view. Additionally, because this approach relies on manual input, the stereo effect may be inconsistent throughout the film sequence, especially when stereo adjustments are applied to a particular scene but not to others.
What is needed is a technique for consistently achieving an optimal stereo effect without the drawbacks of the traditional approaches discussed above.